cp's OEIS Frontend

A376849 Numbers k such that psi(k + psi(k)) = psi(k) + psi(psi(k)), where psi = A002322.

%I A376849 #12 Oct 08 2024 07:19:15
%S A376849 2,5,10,34,80,111,196,204,222,328,351,646,654,704,837,876,935,943,969,
%T A376849 1053,1100,1140,1220,1224,1372,1408,1526,1824,1864,2368,2496,2511,
%U A376849 2715,2816,2842,3159,3294,3528,3648,3672,4332,4473,4600,4736,4992,5500,5632,6325,6528,7296,7412,7512,7533,7832,7959
%N A376849 Numbers k such that psi(k + psi(k)) = psi(k) + psi(psi(k)), where psi = A002322.
%H A376849 Robert Israel, <a href="/A376849/b376849.txt">Table of n, a(n) for n = 1..1000</a>
%e A376849 a(3) = 10 is a term because psi(10) = 4, psi(4) = 2, and psi(10 + 4) = psi(14) = 6 = 4 + 2.
%p A376849 filter:= proc(k) uses numtheory; local s;
%p A376849  s:= lambda(k);
%p A376849  lambda(k+s) = s + lambda(s)
%p A376849 end proc:
%p A376849 select(filter, [$1..10000]);
%t A376849 Select[Range[8000], CarmichaelLambda[ #+CarmichaelLambda[#]] == CarmichaelLambda[#]+CarmichaelLambda[CarmichaelLambda[#]] &] (* _Stefano Spezia_, Oct 07 2024 *)
%Y A376849 Cf. A002322, A376830, A376831, A376843, A376844, A376848, A376851.
%K A376849 nonn
%O A376849 1,1
%A A376849 _Robert Israel_, Oct 06 2024